Nozzle question



But you HAVE competitors.
This market is "managed".

Point.
To form a monopoly for the SELLERS, who author the rules?
Just a guess from a guy who was IN THE ROOM at the time the rules were INSTALLED.
Jerry

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Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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Jerry Irvine wrote:

Are you taking responsibility?
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Have you seen the 'A10' data? According to the NAR datasheet its actually an A2.35
Then again, in some cases, the 'NAR'-style designation may itself be misleading - for example in the case of an extremely regressive or progressive motor, where the thrust at ignition is significantly different from the average thrust figure.
Hybrids motors also have more complex thrust curves - the thrust during the liquid N20 part of the burn is often higher than the average, which is 'brought down' by the portion of the burn where gaseous N20 is contained in the tank.
For example, the HT J330 (835CC172JFX) has a thrust of around 500N at ignition which only drops to 330N just before the gaseous (blowdown?) phase begins.
Have a look at www.thrustcurve.org - quite interesting.
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Niall Oswald
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The A10 has a very large spike from its core, followed by a long low sustainer. If it were marked an A2, unsuspecting users would shread models, and especially BGs. The 10 represents the spike, which contains about 50% of the total impulse.
Several old FSI motors were similar; a big spike followed by a long low thrust sustainer. The D18 is the classic example, but even motors like the D20, E60, and F100 exhibited some of that. So did the Rocketflite BP motors.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
Men never do evil so completely and cheerfully as when they do it with religious conviction. -- Blaise Pascal
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Bob Kaplow wrote:

OK, so what formula is being used to arrive at the '10' number? There ought to be some way of correlating the numeric value assigned to a motor to the thrust levels. Is it supposed to be some percentage of 'peak'? Is it some weighted value of peak*time vs. sustain*time? One ought to be able to determine SOMETHING from the designations.
David Erbas-White
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The number is supposed to be the motor's average thrust. In the case of the A10, and some of the old FSI motors, it's the average of the spike, ignoring the sustainer thrust. Although in the case of the A10, even that isn't enough: the spike alone would be a 7 not a 10.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
Men never do evil so completely and cheerfully as when they do it with religious conviction. -- Blaise Pascal
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Arbitrary label assigned by the Manufacturer.
As allowed by NAR and NFPA rules.

That's phunnie!
Good thing willing manufacturers are banned at the same time!

In case you have not figured it out yet, all these rules are arbitrary.
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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Jerry Irvine wrote:

Are you a manufacturer?
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jerry: more bogus information: the requirements for a motor to be certified is laid out pretty clear in NFPA 1125: the fact that neither Estes not the NAR will correct the labeling speaks volumes about the NAR-Estes non-relationship and the NAR S&T motor certification service program failings......
shockie B)

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IF as you say, they are violating current NFPA-1125 regulation, then they are committing crimes in some 32 states, right?
So why have they not been approached, or why have they not taken preemptive action to correct?
I say it is because the regs as written ALLOW them to call the motor whatever they want.
If not then both AT and Estes and likely Quest are in violation.
You just wiped out all of the industry that TRA/Rogers/Kelly/Rosenfield didn't under HPR.

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Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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I'm not saying "they" whoever "they" are ......are violating anything.....U R....
whats the penalty for mislabeling of rocket motors? none that I am aware of..... just because certain model rocket motors(or for that matter HPR) may be out of spec to NFPA 1125 does not mean that it is the certifying orgs responsibility to correct such mislabeling..... so who is the AHJ here? the state fire marshal of each state? the CPSC? ...
shockie B)

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Since I have no idea what NFPA 1125 specifically says about the labeling, what, exactly, does it say?
If the wording is 'open' enough, it could end up meaning any of several things. For example, the difference between mean, median, and mode (any of which could be picked as 'average', if that is the word used).
David Erbas-White
shockwaveriderz wrote:

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There has been mention in the past of the average of the "usable" or "non-negligable" thrust. The FSI motors with big spikes and long low thrust tails (hardly "sustaining thrust" since they fell out of the air unless you built light) and the A10 mini motor were often cited.
Not sure about the A8.
They did FORCE FAI to change the F100 to the F80 since 100 was both a lie and over the NFPA average thrust limit for a Model Rocket motor.
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-Fred Shecter
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There is a 5% (of peak thrust) threshold and a 10% threshold.

FSI is gone due to compliance issues not commercial issues. And that was in the late 80's.

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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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wrote:

That part is mostly false.

This part is mostly true.
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NAR playing around with the labeling and certifications is an example.
Details in this very thread.
DOT also was changing the treatment of large BP motors (7887 was a reply), but FSI just mailed their motors.

--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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wrote:

That part is almost entirely false.

This part is mostly true.

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david: as far as I can tell NFPA 1125 only says the following:
8.1.3 Model rocket motors, motor-reloading kits, and components offered for sale, exposed for sale, sold, used, or madeavailable to the public shall be examined and tested to determine whether they comply with the standards and requirements detailed in 8.1.7.
8.2.3 High power rocket motor, motor-reloading kit, and components offered for sale, exposed for sale, sold, used, or
made available to the public shall be examined and tested to determine whether they comply with the standards and requirements
detailed in 8.2.7.
so 8.1.7 and 8.2.7 say the same thing:
8.1.7 Before granting such certification, samples of a motor or reloadable motor system shall be examined as follows:
(1) Static testing, conducted at or corrected to sea level and 20C 5C (68F 9F), of a minimum of 10 samples to
determine that total impulse, average thrust, and delay time comply with the following requirements:
(a) Standard deviation of the total impulse data shall be no greater than 6.7 percent of the mean measured value.
(b) No time delay shall be measured to have a variation greater than 1 second or 20 percent (whichever is
greater, but not to exceed 3 seconds) from the labeled value.
(c) Average thrust shall be within 20 percent (or 1 N, whichever is greater) of the average thrust that is
computed by dividing the mean total impulse measured during propellant burn time by the mean propellant
burn time.
(2) For metal-casing reloadable motors, rupture testing of 1 sample to ensure that the casing complies with the burst
pressure and longitudinal failure mode requirements of 7.4.4
(3) Thermal testing to ensure that the casing temperature during and after static firing complies with 7.4.1
(4) Heat sensitivity testing to ensure that the motor or motorreloading kit complies with 7.1.2
(5) Examination of the packaging, marking, and instructions to verify compliance with all provisions of 7.12 through
7.14
(c) Imprinted average thrust shall be within 20 percent
(or 10 N, whichever is greater) of the average thrust
that is computed by dividing the mean total impulse
measured during propellant burn time by the mean
propellant burn time.
(2) For metal-casing reloadable motors, rupture testing of
one sample to ensure that the casing complies with the
burst pressure and failure mode requirements of 7.4.3
and 7.4.4
(3) Thermal testing to ensure that the casing temperature
during and after static firing complies with 7.4.1
(4) Heat sensitivity testing to ensure that the motor or motorreloading
kit complies with 7.1.2
(5) Examination of the packaging, marking, and instructions
to verify compliance with all provisions of 7.12 through 7.24..
so 8.17/8.27 both point to 7.12 through 7.24:
7.13 Rocket Motor Marking.
7.13.1 A rocket motor or motor-reloading kit shall have imprinted on its external surface, casing, or wrapper, a recognized
code indicating the nominal performance parameters - for example, "C6-5" [for a model rocket motor having a
total impulse of 5.01 to 10.0 N-sec (1.1 to 2.2 pound-seconds), an average thrust of 6 N and a time delay of 5 seconds] or
"5-second time delay module" (for a time delay module having a time delay of 5 seconds) - and the date of manufacture or
equivalent coding.
Exception: If the size, shape, or surface of the rocket motor does not permit the required designation to be printed on it, then the equivalent
coding shall be printed on the packaging.
7.13.2* Rocket motors, motor-reloading kits, and pyrotechnic
components shall be marked with information complying with
the Federal Hazardous Substances Act, 16 CFR 1500.
Exception: If the size, shape, or surface of the rocket motor does not
permit the required information to be printed on it, then the information
shall be printed on the packaging.
so 7.13 references 16 CF 1500. and the relavent part is:
Sec. 1500.83 Exemptions for small packages, minor hazards, and special circumstances (36) Individual toy rocket propellant devices and separate delay train and/or recovery system activation devices intended for use with premanufactured model rocket engines are exempt from bearing the full labeling required by section 2(p)(1) of the act (repeated in Sec. 1500.3(b)(14)(i)) insofar as such requirements would be necessary because the articles are flammable or generate pressure, provided that: (i) The devices are designed and constructed in accordance with the specifications in Sec. 1500.85(a) (8) or (9): (ii) Each individual device or retail package of devices bears the following: (A) The statement ``WARNING--FLAMMABLE: Read instructions before use''; (B) The common or usual name of the article; (C) A statement of the type of engine and use classification; (D) Instructions for safe disposal; and (E) Name and place of business of manufacturer or distributor; and (iii) Each individual rocket engine or retail package of rocket engines distributed to users is accompanied by an instruction sheet bearing complete cautionary labeling and instructions for safe use and handling of the individual rocket engines.
...Type of Engine and Use classification... <--what does this mean?
shockie B)

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The DELAY is related to the labeled value.

Has that test EVER been done?

Smoking gun.

Has that test EVER been done?

Clearly has NOT, repeat NOT, been done.

Is the "proper" labeling anywhere in the Estes, Quest, or Aerotech by RCS instructions (packaging) to make up for the fact it is NOT on the casing for sure??

That leaves out HPR entirely.
"Please bring common sense back to rocketry administration. (too late)"

A definition that literally no longer exists.

--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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shockwaveriderz wrote:

Well, I went back and looked at the A10, the A8, and the B6 for some comparisons, and here's what I 'think' is going on. The A10 and A8 have extremely low thrust tails, and they are 'effectively ineffective'. IF you change your assumptions such that 'propellant burn time' ends when the 'effective thrust' ends, then you can, indeed, come up with an A10 and A8 as average thrust values (bear in mind that I'm eyeballing the area under the curve, but that is ROUGHLY what it looks like). In other words, there appears to be some thrust level below which the engine is considered ineffective, and even though there is some small thrust occurring, it is so small as to be ignored.
You can look at a comparison of the A8 and B6 thrust curves to see just exactly what this means -- the A8 has a tail of about 2.3 newtons, and the B6 has a tail of about 4.5 newtons (almost twice as much!). So, the tail portion of a B6 comes to a substantial percentage of the 'average rated' thrust, thus it is actually a 'sustaining thrust'. The A8 has a sustaining thrust of about 33% of the 'average rated' thrust, and so it is not doing much for 'sustaining'.
I'm sure somewhere in the Estes labs is some document that defines all this, and there must be some kind of understanding with NAR S&T as well. For example, I can well imagine that somewhere it is defined that the sustaining thrust must be > 50% of the 'average' thrust for it to be considered 'effective', and that propellant burn time is considered 'complete' at that point.
My point is that by choosing the definitions (and the above are not unreasonable definitions), one can drastically affect the measurement. NAR is making the motor thrust curves and is basing their values on the measurements they have made. There is also nothing in the code that defines the accuracy of the equipment being used. If Estes, for example, has their equipment 'calibrated' differently (i.e, if their sensor shows no propellant burn after .2 seconds), it could simply be that they placed the threshold for that measurement at a higher level.
To add fuel to the fire (pun intended), there must be SOME thrust occurring from the delay charge. It may be small, but it's measurable. This simply points out the fact that one has to draw the line SOMEWHERE.
One last 'factor' in all of this -- we also don't know (precisely) how long the propellant burn is. We are measuring the thrust, not the propellant burn time. If the pressurization/nozzle size has an effect on how long it takes for the gas to escape from the pressure chamber, it would stand to reason that the propellant has stopped burning at some point PRIOR to the thrust dropping to (near) zero. I don't know what that exact number is, but it may have been factored into some of the equations as well.
The bottom line (realistically) is that the numbers given (A10, A8) actually DO tend to reflect the usefulness of the motor, and their true capability for placement in a rocket. Therefore (looking at the results), there probably were/are valid reasons for the above cutoff levels to have been defined.
David Erbas-White
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